42 IBUs seems much to me, too. You generally want to match the gravity to the IBUs in terms of where in the range you go. For instance, If you are at the low end of the OG range, you want to be at the low end of the IBU range too. Same with matching middle and high end of each range. That helps keep the balance in check.
As mentioned, traditionally, Munich & Vienna were used instead of 2 row, and you want to go with debittered black malt instead of black patent. This seems more like an Imperial Robust porter or even a stout as opposed to a Baltic. Doesn't mean it won't be good. Just means that it will be at the edges of the style, and that's ok.
Don't let anyone discourage you. The important thing is to make it and taste it and adjust the things that you want to change. The more practice you get doing that, the easier it becomes to think of a target and put together the ingredients that will hit that. Even then, there are times that the mix tastes nothing like what you thought it would, but it ends up being even better than what you were aiming for.
Enjoy!